This invention relates to an ignition coil for an internal combustion engine.
FIG. 12A is a diagram illustrating an ignition device using a conventional ignition coil for an internal combustion engine. Reference numeral 91 denotes a computer; 3, a switching assembly connected to the computer 91; 58, an ignition coil connected to the switching assembly 3; 4, an electronic device having an additional function and connected to the switching assembly 3; 96, a bracket for mounting the switching assembly 3, the ignition coil 58, and the electronic device 4 thereon; 95, a bolt for fixing the ignition coil 58 to the bracket 96; and 94, a wire harness for connecting the switching assembly 3, the ignition coil 58, and the electronic device 4. FIG. 12B is a cross-sectional view illustrating the ignition coil 58.
Referring to FIG. 13, a description will be given of the operation. An ignition signal processed and output by the computer 91 in correspondence with the position of a crankshaft of an engine is received by the switching assembly 3. The switching assembly 3 is repeatedly turned on and off by the ignition signals, whereby a primary current to a primary winding 51 of the ignition coil 58 is supplied or interrupted. When the primary current is interrupted, a high voltage is generated across both ends of a secondary winding 52 by an induced electromotive force via a core 55. The generated high voltage is supplied to an ignition plug 92 by a high-tension cord (not shown), is discharged in a plug gap, and ignites an air-fuel mixture compressed in a combustion chamber of the engine. It should be noted that the electronic device 4 has the additional function of sending back to the computer 91 a confirmation signal as to where or not the proper primary current is flowing in correspondence with the state of current flowing across the primary winding 51.
Since the conventional ignition device for a multi-cylinder internal combustion engine is comprised of the switching assembly, the electronic device with an additional function, the bracket, the wire harness, and the plurality of ignition coils, there have been problems in that its size and weight are large, the assembly is complicated, there is a possibility of an erroneous connection being made, and the reliability of the electrical connections is low, and that the device is expensive as a result.